PROJECT SUMMARY/ABSTRACT Total Knee Replacement (TKR) is the most successful intervention to address pain from knee osteoarthritis. However, most resume a sedentary lifestyle gain weight and subsequently remain at high risk for poor health outcomes after surgery. There is a critical need for people after TKR to adopt an active lifestyle. Outpatient Physical therapy (PT) is an ideal, low-cost setting for a physical activity intervention for people after TKR given that physical therapists are experts at prescribing and personalizing exercises to meet patients' abilities over multiple outpatient visits. Unfortunately, little study has been devoted to the efficacy of a physical therapist delivered physical activity intervention. The objective of this proposal, which builds on significant preliminary data, is to evaluate the preliminary efficacy over 3 months of a physical therapist-delivered physical activity intervention. The intervention starts with providing a Fitbit? monitor at admission to PT. Next, the physical therapist provides face-to-face feedback on current activity levels and recommends step goals personalized to previous activity levels, a process that takes < 5 minutes at each visit. The intervention is integrated into standardized outpatient PT for TKR. Our team's long-term research goal is to test the efficacy of this innovative intervention in a future multi- center clinical trial.